1. Field of the Invention
The present invention relates to a control device of an injection molding machine and especially relates to a control device of an injection molding machine having a resin purge function.
2. Description of the Related Art
In an injection molding machine, before a molding operation is started, when a color or a type of resin is replaced to perform molding, or when an operation is resumed after the operation is interrupted, a purge operation in which old resin which remains in an injection cylinder is discharged to be replaced with new resin is performed. Further, after an end of the molding operation as well, an operation in which resin remaining in the injection cylinder is discharged by the purge operation so as to prepare for the next operation is performed.
Further, there is a case in which the purge operation is regularly performed from interruption of the molding operation to resumption of the molding operation. Accordingly, resin remaining in an injection cylinder is prevented from turning yellow or being carbonized due to thermal degradation.
As the purge operation, there is a method in which a screw is rotated while being moved forward and backward by a preset injection stroke so as to repeat plasticization and discharge of resin. At this time, if an interval of the purge operation is large and a purge amount in one purge operation is insufficient, yellowing and carbonization of resin caused by thermal degradation of resin may be generated. Inversely, if an interval of the operation is too small, the purge operation is excessively performed beyond necessity. Accordingly, a consumption amount of resin is increased and production cost may be increased disadvantageously.
In Japanese Patent Application Laid-Open No. 10-272664, a technique related to a purging means which stores a first purging condition for performing normal purging (purge operation) and a second purging condition for performing purging before continuous molding in a memory so as to perform purging in accordance with a purging condition which is read out is disclosed. Further, it is also disclosed that respective purging conditions are preliminarily set and stored in the memory.
In Japanese Patent Application Laid-Open No. 2010-223187, such technique is disclosed that an operation condition corresponding to a molding condition related to molding after start of an operation is set when the operation is started after operation interruption of an injection molding machine and a purge operation for discharging resin in a heating cylinder to the outside in accordance with the operation condition is performed predetermined shot times when the operation is started. Further, it is also disclosed that time of at least one molding cycle in execution of molding in accordance with the molding condition is preliminarily set as the operation condition.
Japanese Patent Application Laid-Open No. 10-272664 and Japanese Patent Application Laid-Open No. 2010-223187 disclose that the purge operation is performed in accordance with the predetermined condition which is preliminarily set. However, the operation condition such as setting time of the purge condition has to be preliminarily set in both cases. Therefore, an operator who is not familiar with the setting operation has difficulty in performing the setting operation and a load of the operation may be imposed even on an operator who is familiar with the setting operation.